Blood was collected from 49 adult woodland caribou (Rangifer tarandus caribou) captured in northern Alberta, Canada, from October to February, 1991 to 1992 and 1992 to 1993. Smears of the buffy coat layer and of whole blood were examined microscopically for Trypanosoma sp., and blood was cultured for latent parasites. Trypanosomes were present in 41 (84%) of 49 cultures 9 days or older, but none was detected in fresh blood. Trypanosomes were pleomorphic, consisting of small oval amastigotes, 2 to 8 μm, intermediate-size epimastigotes, 20 to 30 μm in total length (including the flagellum), and large trypomastigotes, 60 to 90 μm length, with pointed ends, a well developed kinetoplast, a long free flagellum, and a prominent undulating membrane. Dividing epimastigotes appeared in pairs or rosettes of five or more organisms. Based on culture characteristics and morphologic features, the organism was identified as Trypanosoma (Megatrypanum) sp.